When you book, look for nonstop flights and remember that "direct" flights stop at least once. Try to avoid connecting flights, which require a change of plane. Two airlines may operate a connecting flight jointly, so ask if your airline operates every segment of the trip -- you may find that the carrier you prefer flies you only part of the way.
The least-expensive airfares are priced for round-trip travel and usually must be purchased in advance. Airlines generally allow you to change your return date for a fee. However, most low-fare tickets are nonrefundable. Always check different routings and look into using alternate airports. Also price off-peak flights, which may be significantly less expensive than others.
When flying within the U.S., plan to stay over a Saturday night and travel during the middle of the week to get the lowest fare